SeeedStudio 101990885, User Manual

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Stop bits: 1
Data bits: 8
Parity: None
8. Communication commands and parameter definitions
8.1 Definition and description of the frame structure
Frame structure definition
Starting
Code
Length of data
Function
codes
Address
code 1
Address
code 2
Data Check Code
0X55 Lenth_L Lenth_H Command Address_1 Address_2 Data Crc16_L Crc16_H
1 Byte 1 Byte 1 Byte 1 Byte 1 Byte 1 Byte n Byte 1 Byte 1 Byte
Starting
Code
Length
of data
Function
codes
Address
code 1
Address
code 2
Data
Check
Code
Frame structure description
a. Start code: 1 Byte, fixed to 0X55.
b. Data length: 2 Byte, low byte before, high byte after. Length = Data
Function Code + Address Code 1 + Address Code 2 + Data + Checksum.
c. Function code: 1 Byte
Read command: 0X01
Write command: 0X02
Passive report command: 0X03
Active report command: 0X04
d. Address code:
Address code 1 indicates the functional classification.
The address code 2 indicates the specific function.
Refer to the address assignment and data information description.
e. Data: n Byte
f. Checksum: 2 Byte, low byte before, high byte after.
CRC16 checksum is used. Refer to Appendix 1 for reference codes